Hemoglobinopathies, such as sickle cell disease (SCD) and thalassemia, are among the greatest public health concerns in the world. Although new therapeutic modalities, such as gene therapy, are currently being tested, a pharmacologic approach is absolutely needed for general patient populations. Our long-term goal is to develop a compound(s) that induces fetal-type globin (HbF) by targeting the transcriptional complex regulating globin switching. The objective of this application is to determine the molecular mechanisms by which the transcription factor LRF (a.k.a. ZBTB7A, Pokemon and FBI-1) represses fetal globin expression in adult erythroid cells. Our central hypothesis is that LRF represses embryonic/fetal globin expression via the NuRD complex in adult erythroblasts. The rationale for the proposed research is that understanding LRF-mediated globin regulation will enhance our understanding of how globin switching is controlled transcriptionally and facilitate development of novel HbF induction therapies. Guided by strong preliminary data, we expect to achieve our objective by pursuing the three specific aims: 1) to determine the molecular basis of embryonic/fetal globin reactivation observed in LRF-deficient erythroblasts; 2) to determine functional relationships between LRF and the NuRD complex in controlling globin switching; and 3) to determine the effects of LRF depletion on SCD pathogenesis in mice. In Aim 1, we will employ ChIP-seq, DNase-seq, digital foot-printing and chromosome conformation capture (Capture-C) to define epigenetic and conformational changes in the globin locus of LRF-deficient erythroblasts. In Aim 2, we will determine how LRF represses embryonic/fetal globin expression mechanistically via the NuRD complex. To do so, we will perform ChIP-seq for LRF, BCL11A, and NuRD components in control- and LRF-deficient erythroblasts and determine functional relationships between LRF and BCL11A using LRF/BCL11A double knockout human immortalized erythroid cells and LRF/BCL11A double conditional knockout mice. In Aim 3, we will determine how LRF depletion alters SCD pathogenesis by employing LRF conditional knockout mice and a humanized mouse SCD model. Our concept, namely that LRF represses embryonic/fetal globin expression through the NuRD complex in adult erythroblasts, is innovative, because we have shown, for the first time, that LRF is a potent repressor of embryonic/fetal globin expression. Our proposed study is significant, because it reveals a novel molecular mechanism governing fetal globin repression in adult erythroid cells and should therefore encourage development of new HbF reactivation therapies.